The altitude to change to Standard altimeter setting varies with location, in Europe it's within 2-3000 ft of the ground, in Latin America it's 20000 ft AGL, in Asia it varies depending on country. In Singapore it's 11000 ft.
Mike Payne On 04/09/2011, at 18:03 , Carleton MacDonald wrote: > As one who used to fly – > > Local altimeter settings (pressure) are intended to have the altimeter in the > airplane roughly approximate the elevation of the runway. So if an airport > is (sorry, it’s what they unfortunately do) 3522 feet above sea level, an > airplane with its altimeter set properly would have an altimeter that reads > about that when the airplane lands. > > Above FL 180 (flight level 180, which is only 18,000 feet if the atmosphere > in that area is standard), everyone sets the altimeters to the standard > atmosphere setting. It may not accurately reflect height above ground, but > more importantly everyone is at the same height with respect to EACH OTHER > which is more important really. > > If actual atmospheric pressure is below standard then FL 180 may not be > usable, as it may be less than 18,000 ft above sea level, and airplanes would > then lose minimum (1000 ft) separation with those below them at 17,000 ft; > those airplanes are using local altimeter settings instead. > > Sorry for the feet but until large parts of the world get their acts together > that’s still how many countries measure height in aviation. > > Carleton > > From: [email protected] [mailto:[email protected]] On Behalf Of > Martin Vlietstra > Sent: Sunday, September 04, 2011 17:40 > To: U.S. Metric Association > Subject: [USMA:51071] Re: planes collide > > I believe that the aviation industry uses air pressure to calibrate > altimeters. Changing the standard atmosphere from 101.325 kPa to 100 kPa > will result in an apparent 130 m difference in reference altitude. I don’t > think that they are willing to take the risk with this change. > > From: [email protected] [mailto:[email protected]] On Behalf Of > Michael Payne > Sent: 04 September 2011 21:27 > To: U.S. Metric Association > Cc: U.S. Metric Association > Subject: [USMA:51069] Re: planes collide > > In 1999, the International Union of Pure and Applied Chemistry (IUPAC) said > that for the purposes of specifying the properties of substances, “the > standard pressure” should be defined as precisely 100 kPa (≈750.01 torr) or > 29.53 inHg rather than the 101.325 kPa value of “one standard atmosphere” > (From Wikipedia). > > I think we're talking about 2 different things here, the Standard Atmosphere > and the International Standard Atmosphere. I know the latter is purely a set > of units set up to calibrate and test things worldwide to the same standard. > 15C, 1 Atmosphere of 1013,25 hPa. It's heavily used in the aerospace industry > for calibration and performance. Everyone has to be on the same page for > these two items. > > A bit more research is needed. > > Mike Payne > > > On 04/09/2011, at 07:39 , John M. Steele wrote: > > > One (standard) atmosphere is 101.325 kPa. However, properties for many > chemicals are specified at 1 bar (100 kPa) rather than 1 atm. There is also > a 'technical atmosphere" 98.0665 kPa (based on kilogram-force), which is now > deprecated and rarely used.. > > --- On Sun, 9/4/11, Michael Payne <[email protected]> wrote: > > From: Michael Payne <[email protected]> > Subject: [USMA:51064] Re: planes collide > To: "U.S. Metric Association" <[email protected]> > Date: Sunday, September 4, 2011, 6:58 AM > > I believe one atmosphere is still 100 kPa, the 1013,25 comes from the > International Standard Atmosphere. > > Commonly referred to as the ISA it's what manufacturers use to calibrate > instruments and what aircraft makers use to calibrate the performance of > aircraft. In the aviation world we constantly refer to the temperature being > below or above ISA, the lapse rate is fixed under ISA as 1.98 C up to 36090 > (11000 m) where it's supposed to be constant. Obviously in the real world it > changes which has an affect on performance. > > Mike Payne > > On 03/09/2011, at 13:57 , G. Stanley Doore wrote: > > > The 1013.25 mbar (101.325 kPa) pressure for altimeter settings is NOT > "arbitrary" as Kilopascal & Wiki write. The standard altimeter setting for > worldwide altimeter settings was determined from the mean surface pressure > level. > Stan Doore > On Sep 3, 2011 11:36 AM, "Michael Payne" <[email protected]> wrote: > >
